JPS584872B2 - SECAM signal video phase adjustment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video phase adjustment method that maintains the video phase when converting a SECAM color television signal to another synchronization system.

The SECAM system is a system that has been put into practical use as a standard color television system along with the NTSC system and the PAL system, and is mainly used in France, the Soviet Union, and other countries.

In the SECAM system, a carrier color signal is generated using an FM signal, and the color difference signals R-Y and B-Y are switched and sent for each scanning line.

Mixing and switching to SECAM signals using studio equipment, etc.
Conventionally, when performing wave, slit, etc. operations, the composite SECAM signal is demodulated and the baseband signal (R, G,
B, or Y, R-Y, B-Y), and after performing the above operations on the baseband signal, a composite SECAM signal was synthesized again.

First, the conventional technology will be explained with reference to FIG.

Input SECAM composite color television signal (INPU
T) is distributed by a distributor and supplied to a low-pass filter (LPF), a band-pass filter (BPF), and a synchronous separation circuit, respectively.

A low-pass filter (LPF) removes the color subcarrier component in order to extract only the luminance signal component.

In this regard, since the color signal component is mixed in the high frequency portion of the luminance signal band, there is a problem that the high frequency component of the luminance signal component is lost by this filter.

At the same time, crosstalk of the color signal to the luminance signal cannot be avoided.

On the other hand, color subcarrier components are extracted by a bandpass filter (BPF).

Here too, contrary to the aforementioned luminance signal, crosstalk of the luminance signal high frequency component to the chrominance signal cannot be avoided.

The separated color subcarrier components are converted into simultaneous signals by a sequential simultaneous conversion circuit that converts the R-Y and B-Y line sequential signals into simultaneous signals by alternately switching between a delay line and a through signal for each line. It is taken out.

At the same time, it is separated into RY and BY.

The separated color signals are demodulated into R-Y and B-Y signals by each demodulator (Table 1).

The above luminance and color difference signals are each processed by an A/D converter. It is converted into a PCM signal.

Each PCM signal is multiplexed by a multiplexing circuit to facilitate memory write and read operations.
written to memory.

The memory has a capacity for one field of input video signal,
Image data for one field of the input signal is stored in accordance with the input side synchronization signal.

The third output of the distributor is input to the sync separator, and only the sync signal is taken out and supplied to the input timing generator.

The input timing generator generates various control pulses, clock pulses, etc. to the write side of the memory.

At the same time, the line discrimination circuit distinguishes the color of the input line (R-
Y line or B-Y line) and sequentially generate simultaneous conversion control pulses to correctly separate color signals.

Signals written into the memory sequentially based on the input side synchronization are read out from the memory using the output side synchronization signal as a reference.

That is, the memory plays the role of an elastic memory that adjusts the phase of the time axis of the video signal for synchronization between the input side and the output side, which have different lengths.

Generally, the memory capacity is 1 field or 1 frame, and when the time error reaches 1 field or 1 frame, the input field or input frame is repeatedly read out or skipped, and the input field or input frame is read out in units of fields or 1 frame. Phase adjustment is performed in frame units.

This example shows the case of one field; unit.

The data read out in this way is again decomposed into three signals: a luminance signal, a color difference signal R-Y, and a BY-Y signal, each of which is restored to an analog signal by a D/A converter, and then converted into a SECAM color composite signal by an encoder. taken as a signal.

The control circuit (WRITE/READ CONTROL) compares the frequency, phase, etc. of input side synchronization and output side synchronization,
The three-output timing generation circuit, which generates various control pulses for controlling reading and writing to the memory by calculation, has exactly the same function as the input timing generation circuit.

As is clear from the above description, in the conventional system shown in FIG. 1, the input signal must be decomposed into three signals and then demodulated.

For this reason, as mentioned above, (1) crosstalk occurs between the luminance signal and the chrominance signal, (2) the system becomes complicated due to the processing of decomposing and demodulating the three signals, and since it is analog processing, it becomes unreliable. It has drawbacks such as reduced performance and signal deterioration.

Furthermore, (3) during sequential and simultaneous conversion, R-Y or B-
Either one of Y is used as a signal delayed by one line.

For example, R-Y of line number 7 in the first field of Table 1
The signal will also be used as line number 8 RY when synchronized.

This causes the center of gravity of the image to shift by one line, resulting in a deviation between the color signal and the luminance signal.

When it is finally taken out as an output, one color signal is discarded when it is converted back into a line sequential signal, but only the color signal is discarded each time a frame is repeated or skipped. This causes a vertical shift of the image center of gravity by one line.

Therefore, an object of the present invention is to improve the above-mentioned drawbacks of the conventional technology, and its characteristics are to digitize a SECAM color television signal as a composite signal, store it in a storage device, and read it out according to an independent synchronization system. This enables video special effects such as wipes and slits, and furthermore, when a field is read twice or skipped, the color difference signal is shifted in units of scanning lines according to a predetermined algorithm.

Examples will be described below with reference to the drawings.

Table 2 is a diagram showing the color arrangement in each line of the SECAM color television signal.

The numbers on the left side indicate line numbers within the field, and the numbers 1, 2, 3, . . . at the top indicate field numbers.

In the figure, for example, line number 7 of the first field indicates that the RY signal exists, and line number 8 of field number 5 indicates that the BY signal exists.

In field synchronization, the video phase is adjusted on a field-by-field basis.

When (input frequency>output frequency), one frame of input is thinned out at that point, thereby performing phase adjustment on a frame-by-frame basis.

When (input frequency<output frequency), one frame of the input frame is read out repeatedly, thereby performing field phase modulation.

In this case, as is clear from Table 1, for example, when (input frequency<output frequency), one input field is used as one output field, and then it may be used repeatedly as two fields.

In this case, for example, line number 8 of the first field of input
If 320 is used as the line number 320 of the second field of output, that is, if each line signal of the first field of input is used as the second field, the color order is maintained in the normal sequence.

Similarly, in the third field, if input line number 8 B-Y is used as line number 7, the normal color order can be maintained.

In this case, if odd and even lines are included in the number, the center of gravity will move up by two lines.

It is clear from the table and above description that the color sequence can be maintained for any other field in exactly the same way.

After several more fields, it is possible that the input field will be used as the field after 4 fields (2 frames), but as is clear from the table, in that case, the color order will be the same as that of the first field. In that case, it is a good idea to return to normal reading (returning the operation of reading out one line early) from what has been read out one line early.

This is because, as is clear from the table, the color sequence completes one cycle in four fields (two frames).

As is clear from the above explanation, the correct color order can always be maintained by repeating the operation from normal read to pre-read, or vice versa, each time reading or repeating occurs, or in other words, each time reading and writing cross. It turns out.

The difference between pre-reading and normal reading is that the number of images is 1 to 3.
The difference between the input frequency and the output frequency is generally very small; for example, C
According to the CIR standard, the maximum allowable limit is 0.001%, so this means that the frequency of repetition is 1 to 1 in several minutes to several tens of minutes.
It means that it only happens once.

The above description deals with the case where (input frequency<output frequency), but it is clear from the table that the same operation can be performed even in the reverse case.

However, in this case, since fields are thinned out, the second field may be used as the first field, and the third field may be used as the first field in the same manner.

This is exactly the same for other fields.

Furthermore, the movement of the center of gravity of the image due to repeated thinning is shown in FIG.

In FIG. 2, the horizontal axis represents time, the vertical axis represents line numbers, and the thick lines represent fields. The solid lines represent repeated fields, and the dotted lines represent thinned fields.

As is clear from Figure 2, in the case of field repetition, the first line is used one line before (n-1), and the second line is one line before (n-2).
is used, and in the third iteration, after 3 lines (n+1
) is used, and in the 4th iteration, the previous line (n) is used to return to the normal state, and when thinning the field, the 3rd line previous (n-3) is used in the first thinning. After that, the line one line later is used every time the line is thinned out, and the normal state is restored at the fourth thinning.

Note that a shift of one line here means one line of each field in interlaced scanning.

Furthermore, considering the phase at the beginning of the subcarrier line, 1
These relationships are not satisfied by the above operation because they go around once every 2 feet, but this subcarrier phase sequence was originally intended for compatibility with black and white receivers, and this relationship is not actually maintained. Opportunities occur only at the moment of frame repetition or thinning, and they only occur once every few minutes to several tens of minutes, so there is no problem at all in practice.

FIG. 3 shows a block diagram of a harmonization device according to the invention.

In FIG. 3, the input video signal applied to the input terminal IN is divided into two parts by a distributor 10, one of which is separated by a synchronization signal by a synchronization separation circuit 17, and is supplied to an input timing generator 18. .

The input timing generator 18 generates various clock pulses and timing pulses necessary for writing to the memory 12.

The other output of the distributor 10 is supplied to the A/D converter 11, where analog-to-digital conversion is performed.

This analog-to-digital conversion is performed on the input SECAM color composite signal as is.

The converted digital SECAM signal is sequentially written into the memory 12 one field at a time in synchronization with the input side.

Writing control is performed by a control circuit 19.

Therefore, the written data is the SECAM color composite signal itself, and the color signal is a line sequential signal.

However, since there is no particular need to store the synchronized portion, generally the portion of the composite video signal excluding the blanking portion is stored.

These written signals are then read out according to the synchronization on the output side, and the video phase adjustment during mutually independent synchronization is this one.
This is done by giving field memory the function of elastic memory.

In the case of repeated readout or intermittent readout in units of field i, which inevitably occurs due to the difference in input and output synchronization frequencies, the following operations are performed.

In the present invention, each time field repetition or thinning occurs, the signal used as output side data is shifted by 1 to 3 lines and 2 periods from the normal case, as explained in FIG.

As a result, on the output side, even if there is repetition or thinning, a signal with the correct color order maintained can be passed around, and the output signal remains as a composite signal with other SECAM signals based on the output side synchronization. Wipe, slit switching, etc. can be performed with 1.

These changes are made using the 1H line, 2H line, and 3H line in Figure 3.
This is done by switching the lines (delay lines) 13a, 13b, 13c and the through line 13a using the switch 14.

The output of the switch 14 is converted into digital/analog by the D/A converter 15, and output-side synchronization is added by the synchronization addition circuit 16 to produce a SECAM composite color television signal whose video phase is adjusted to the normal output-side synchronization. is the output terminal OU
Obtained in T.

In this embodiment, a method is adopted in which the line shift registers 13a to 13c and the through line are switched on the memory reading side, but by reading out the through line and the lead or delay signal of the line in parallel when reading the memory, It is also possible to omit the line shift registers 13a to 13c.

In addition, in the above embodiment, writing is performed by writing only the video part excluding the synchronized part to the memory and adding synchronization on the output side. Of course, it is also possible to omit the synchronous addition.

Finally, the effects specific to the present invention are listed below.

(1) Compared to the conventional method shown in FIG. 1, the system is simpler and there are fewer analog processing parts, which is advantageous in terms of reliability and signal deterioration.

(2) Since the SECAM composite signal is directly processed, no crosstalk occurs between the luminance signal and the chrominance signal.

(3) In the conventional method shown in FIG. 1, the centroid positions of the luminance signal and color signal are shifted by one line, but according to the method of the present invention, the centroid positions of the luminance signal and chrominance signal completely match.

(4) Since image processing is performed in units of fields, the memory capacity is smaller than in the case of processing in units of frames.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a SECAM color television signal phase modulator according to the prior art, FIG. 2 is an explanatory diagram of the movement of the image center of gravity according to the present invention, and FIG. 3 is a SECAM color television signal phase modulator according to the present invention. This is the block diagram of 10...Distribution circuit, 11...A/D converter, 12...Memory (storage device), 13...
...Line shift register, 14...Switcher, 15...D/A converter, 16...
Synchronization addition circuit, 17... Synchronization separation circuit, 18.
...Input timing generation circuit, 19...
control circuit, 20...output timing generation circuit,
21...Reference synchronization signal.

Claims (1)

[Claims] 1. Converting an input SECAM color television signal including a luminance signal and a chromaticity signal into a digital signal, storing the digital signal for one field or more in a storage device according to an input synchronization signal, and converting the contents of the storage device into a digital signal according to the input synchronization signal. When an event occurs in which the same field is read out repeatedly or a field is skipped, each time an event occurs, one line ahead, Shift the horizontal scanning line 1 line ahead, 3 lines later, and 1 line ahead, and in the case of skip, shift the horizontal scanning line 3 lines ahead, 1 line later, 1 line later, and 1 line later each time an event occurs. The S-ECAM color television is characterized in that the color signal line sequential characteristic of the SE-CAM signal is maintained correctly before and after storage in a storage device by shifting the output and converting the output into an analog signal and outputting the same. Video phase adjustment method for signals.